During the motor rotor control process, it is necessary to detect the rotor position. The existing technology uses a revolver to detect rotor rotational position and send out a simulation signal. The digital signal quantity is calculated through a specific decoding chip. The vehicle speed can be calculated by the ECU of the electric vehicle based on the current position signal and the previous position signal. Moreover, the necessary increase in driver voltage for the electric motor rotor can be computed. Through these procedures, the driver signal for the revolver can be determined. Thus the revolver can provide the preset three-phase AC voltage to the stator winding of the electric motor based on the driver signal.
However, since other unpreventable external electromagnetic interferences can cause the rotor position data to have a greater error or even be incorrect, if the electric motor control ECU does not further check the position signal and provide the control signal based on the current sampled position signal, it can be very dangerous and may lead to serious consequences. But at the same time, the ECU must also exert control over the electric motor. If the current data is discarded and the control of the electric motor ceases, it can also cause the electric motor to lose control. Thus, it is necessary to have control methods that are continual and reasonable in managing these potential situations when they occur.
Furthermore, in automobile production, it is easy to make a mistake in positioning the angle of the revolver used to detect the position of the motor rotor. In the process of dealing with an erroneous revolver position angle, the revolver position angle needs to be examined. The existing technology solves the issue by comparing the last sampled position angle with the current position angle to determine if the difference is within a reasonable range. Since the electric motor rotor position angle cannot have a large increase occurring within a short period of time, thus it can determine whether the current sampled rotor position is correct or not.
If the position angle signal changes suddenly, then the sampled position angle is considered incorrect and the current sampled position angle signal is discarded. Then a different strategy is employed to deal with the erroneous angle where a correct speed value obtained based on the last sampled rotor position is used to correct the current sampled speed value resulting in a corrected current rotor position angle. Lastly the correcting value is used to control the electric motor.
When the motor rotor position continues to be in error, although this type of method can process the rotor error, but in this process, the accumulated errors resulted from the calculations for the rotor positions may lead to a larger difference between the correct rotor position sampled after the revolver returns to normal operation and the related calculated rotor position. If this particular sampled correct rotor position is used to control the motor, then the motor rotation speed may have a increase that can lead to an overly large electric current resulting in damage to power components.